rsync.net will pay USD $500 for about:tabs to exist in mainline firefox with no extension required.
It couldn't be simpler - you type about:tabs into the URL bar and you get a non-html plain text listing, one URL per line, of all the tabs you have open. Maybe a line break inbetween browser windows so you can tell tabs from one window apart from tabs in another ?
Just email info@rsync.net to claim this.